Extraction of muscle proteins and gelatine from cod head

A simple method to extract proteins from minced cod head by mild chemical treatment has been developed. The major part of muscle proteins was recovered by successive extraction at room temperature in dilute NaOH (pH 11) and HCl (pH 2–2.6). Gelatine was extracted at acid conditions and elevated temperatures from residual connective tissues and bones. Almost half of the total protein (47.5%) was extracted from muscle and soft tissues, whereas 12% were recovered as gelatine from soft connective tissues and bones. Functional properties of the various gelatine fractions were compared with functional properties of gelatine extracted from cod skin. Gelatine extracted from soft head connective tissues had similar molecular weight, viscosity and gel strength as gelatine from cod skin. The higher temperatures and stronger acidity necessary to extract gelatine from the head bones, resulted in more hydrolyzed gelatine with poor gelling properties, but still viscosities were only moderately lower than the viscosity of gelatine extracted from soft connective tissues.